Our objective is to define more precisely the lower end of the dose-response curve of sulfur oxides and particulates in human populations. We plan to study a random sample of adults and a majority of the lower elementary grade school children in six different sites. Health effects will be assessed by standard questionnaire on respiratory symptoms and simple tests of pulmonary function. Air monitoring will be done in each area. The differences between communities will be examined and it is anticipated that some of the communities will have changes in their levels of pollution so that we can then see what effect, if any, the change has had on the health of the population. The adults will be restudied at three-year intervals, and the children annually.